video downloads Phase A: cancelled state, cancel/retry, monitor robustness

Fixes the 'cancelled but still shows running' stuck bug and adds real depth:
- classify_state now distinguishes 'cancelled' from 'failed'.
- Monitor is robust to slskd forgetting a transfer: if it's gone, it first tries to
  complete from the FILE on disk (survives the music 'Clean Completed Downloads'
  auto-clear), else counts misses and fails the row after ~8 polls instead of hanging
  on 'downloading' forever. Cancelled transfers → cancelled status.
- POST /downloads/cancel (slskd DELETE transfer + mark cancelled) and /downloads/retry
  (re-grab the same release). get_video_download(id) added; clear includes cancelled.
process_download stays pure (fs/slskd injected); 15 tests, ruff + guard clean.
Phase B (page: tabs/queue/history/cancel+retry buttons) next.

api/video/downloads.py

@@ -276,6 +276,45 @@ def register_routes(bp):
         ensure_started(get_video_db)   # also (re)start the monitor when the page is open
         return jsonify({"downloads": db.list_video_downloads()})
 
+    @bp.route("/downloads/cancel", methods=["POST"])
+    def video_downloads_cancel():
+        from . import get_video_db
+        from core.video.slskd_download import cancel_download
+        body = request.get_json(silent=True) or {}
+        db = get_video_db()
+        dl = db.get_video_download(body.get("id"))
+        if not dl:
+            return jsonify({"ok": False, "error": "Download not found."}), 404
+        if dl["status"] in ("completed", "failed", "cancelled"):
+            return jsonify({"ok": True, "already": True})
+        cancel_download(dl.get("username"), dl.get("filename"))   # best-effort; mark regardless
+        import time
+        db.update_video_download(dl["id"], status="cancelled", error="Cancelled",
+                                 completed_at=time.strftime("%Y-%m-%d %H:%M:%S"))
+        return jsonify({"ok": True})
+
+    @bp.route("/downloads/retry", methods=["POST"])
+    def video_downloads_retry():
+        """Re-grab the SAME release (basic retry). Auto-retry + alternate-query retry
+        come in a later phase."""
+        from . import get_video_db
+        from core.video.download_monitor import ensure_started
+        from core.video.slskd_download import start_download
+        body = request.get_json(silent=True) or {}
+        db = get_video_db()
+        dl = db.get_video_download(body.get("id"))
+        if not dl:
+            return jsonify({"ok": False, "error": "Download not found."}), 404
+        if not dl.get("username") or not dl.get("filename"):
+            return jsonify({"ok": False, "error": "Nothing to retry from."}), 400
+        started = start_download(dl["username"], dl["filename"], dl.get("size_bytes") or 0)
+        if not started.get("ok"):
+            return jsonify({"ok": False, "error": started.get("error") or "slskd refused the download."}), 502
+        db.update_video_download(dl["id"], status="downloading", progress=0, error=None,
+                                 dest_path=None, completed_at=None)
+        ensure_started(get_video_db)
+        return jsonify({"ok": True})
+
     @bp.route("/downloads/clear", methods=["POST"])
     def video_downloads_clear():
         from . import get_video_db

core/video/download_monitor.py

@@ -30,21 +30,12 @@ _started = False
 _lock = threading.Lock()
 
 
-def process_download(dl: dict, transfers: list, download_dir: str, *, lister, mover) -> dict | None:
-    """Decide the next state for one active download given the current slskd transfers.
-    Returns a patch dict for the DB row (or None to leave it untouched this tick)."""
-    t = find_transfer(transfers, dl.get("username"), dl.get("filename"))
-    if not t:
-        return None                                  # not registered yet (or cleared) — wait
-    state = classify_state(t.get("state"))
-    if state == "active":
-        return {"status": "downloading", "progress": progress_pct(t)}
-    if state == "failed":
-        return {"status": "failed", "error": "Soulseek transfer " + str(t.get("state") or "failed")}
-    # completed → locate the file on disk and move it into the library folder
+def _complete_via_file(dl, download_dir, lister, mover):
+    """Locate the finished file in the download dir and move it to the library. Returns
+    a completed/failed patch, or {'progress':100} if the file isn't there yet."""
     src = find_completed_file(download_dir, dl.get("filename"), lister)
     if not src:
-        return {"progress": 100.0}                   # slskd done; file still settling — retry
+        return {"progress": 100.0}
     dest = dest_path_for(dl.get("target_dir"), src)
     try:
         mover(src, dest)
@@ -53,6 +44,29 @@ def process_download(dl: dict, transfers: list, download_dir: str, *, lister, mo
     return {"status": "completed", "progress": 100.0, "dest_path": dest}
 
 
+def process_download(dl: dict, transfers: list, download_dir: str, *, lister, mover) -> dict | None:
+    """Decide the next state for one active download given the current slskd transfers.
+    Returns a patch dict for the DB row, or {'_missing': True} when slskd no longer
+    knows the transfer (the caller decides when to give up). Robust to slskd clearing
+    completed transfers (the music 'Clean Completed Downloads' automation) by also
+    detecting completion from the file landing on disk."""
+    t = find_transfer(transfers, dl.get("username"), dl.get("filename"))
+    if not t:
+        # slskd forgot it — could be done+cleared. If the file's there, finish it.
+        done = _complete_via_file(dl, download_dir, lister, mover)
+        if done.get("status"):
+            return done
+        return {"_missing": True}
+    state = classify_state(t.get("state"))
+    if state == "active":
+        return {"status": "downloading", "progress": progress_pct(t)}
+    if state == "cancelled":
+        return {"status": "cancelled", "error": "Cancelled on Soulseek"}
+    if state == "failed":
+        return {"status": "failed", "error": "Soulseek transfer " + str(t.get("state") or "failed")}
+    return _complete_via_file(dl, download_dir, lister, mover)   # completed
+
+
 def _move(src: str, dest: str) -> None:
     os.makedirs(os.path.dirname(dest) or ".", exist_ok=True)
     shutil.move(src, dest)
@@ -64,23 +78,46 @@ def _walk(root: str):
             yield os.path.join(dirpath, f)
 
 
+_GIVE_UP_AFTER = 8       # consecutive 'transfer gone, no file' polls before failing it
+_misses: dict = {}       # download id -> consecutive missing polls
+
+
 def _tick(db) -> None:
     active = db.get_active_video_downloads()
     if not active:
+        _misses.clear()
         return
     from config.settings import config_manager
     download_dir = str(config_manager.get("soulseek.download_path", "") or "")
     transfers = list_downloads()
+    live_ids = set()
     for dl in active:
+        live_ids.add(dl["id"])
         upd = process_download(dl, transfers, download_dir, lister=_walk, mover=_move)
         if not upd:
             continue
-        if upd.get("status") in ("completed", "failed"):
+        if upd.get("_missing"):
+            # slskd no longer has the transfer and the file never appeared. Give it a
+            # few polls (a just-cancelled transfer vanishes), then mark it failed so it
+            # doesn't sit on 'downloading' forever.
+            n = _misses.get(dl["id"], 0) + 1
+            _misses[dl["id"]] = n
+            if n >= _GIVE_UP_AFTER:
+                _misses.pop(dl["id"], None)
+                db.update_video_download(dl["id"], status="failed",
+                                         error="Soulseek transfer disappeared",
+                                         completed_at=time.strftime("%Y-%m-%d %H:%M:%S"))
+            continue
+        _misses.pop(dl["id"], None)
+        if upd.get("status") in ("completed", "failed", "cancelled"):
             upd.setdefault("completed_at", time.strftime("%Y-%m-%d %H:%M:%S"))
         try:
             db.update_video_download(dl["id"], **upd)
         except Exception:
             logger.exception("video download %s: failed to persist update", dl.get("id"))
+    # drop miss counters for ids that are no longer active
+    for k in [k for k in _misses if k not in live_ids]:
+        _misses.pop(k, None)
 
 
 def _run(db_provider) -> None:

core/video/slskd_download.py

@@ -71,17 +71,40 @@ def flatten_downloads(data: Any) -> list:
 
 
 def classify_state(state: Any) -> str:
-    """slskd state string → 'completed' | 'failed' | 'active'. Pure."""
+    """slskd state string → 'completed' | 'cancelled' | 'failed' | 'active'. Pure."""
     s = str(state or "").lower()
     if "completed" in s and "succeed" in s:
         return "completed"
-    if any(x in s for x in ("error", "cancel", "timed", "failed", "reject")):
+    if "cancel" in s:
+        return "cancelled"
+    if any(x in s for x in ("error", "timed", "failed", "reject")):
         return "failed"
     if "completed" in s:        # completed but not succeeded → treat as failed
         return "failed"
     return "active"
 
 
+def cancel_download(username: str, filename: str) -> dict:
+    """Cancel (and remove) a slskd transfer matching username+filename. Returns
+    {ok[, gone][, error]}. 'gone' = the transfer was already absent."""
+    base, headers = _conn()
+    if not base:
+        return {"ok": False, "error": "slskd isn't configured"}
+    tid = None
+    for t in list_downloads():
+        if t.get("username") == username and t.get("filename") == filename:
+            tid = t.get("id")
+            break
+    if not tid:
+        return {"ok": True, "gone": True}
+    try:
+        requests.delete(base + "/api/v0/transfers/downloads/%s/%s" % (quote(str(username or "")), tid),
+                        headers=headers, params={"remove": "true"}, timeout=10)
+        return {"ok": True}
+    except Exception as e:   # noqa: BLE001 - surface the failure; the row is marked cancelled anyway
+        return {"ok": False, "error": str(e)}
+
+
 def progress_pct(transfer: dict) -> float:
     """0–100 from bytesTransferred/size (100 once completed). Pure."""
     transfer = transfer or {}
@@ -101,4 +124,4 @@ def find_transfer(transfers: list, username: str, filename: str) -> dict:
 
 
 __all__ = ["start_download", "list_downloads", "flatten_downloads", "classify_state",
-           "progress_pct", "find_transfer"]
+           "progress_pct", "find_transfer", "cancel_download"]

database/video_database.py

@@ -1158,6 +1158,14 @@ class VideoDatabase:
         finally:
             conn.close()
 
+    def get_video_download(self, dl_id: int) -> dict | None:
+        conn = self._get_connection()
+        try:
+            row = conn.execute("SELECT * FROM video_downloads WHERE id = ?", (int(dl_id),)).fetchone()
+            return dict(row) if row else None
+        finally:
+            conn.close()
+
     def get_active_video_downloads(self) -> list:
         conn = self._get_connection()
         try:
@@ -1185,7 +1193,7 @@ class VideoDatabase:
     def clear_finished_video_downloads(self) -> int:
         conn = self._get_connection()
         try:
-            cur = conn.execute("DELETE FROM video_downloads WHERE status IN ('completed', 'failed')")
+            cur = conn.execute("DELETE FROM video_downloads WHERE status IN ('completed', 'failed', 'cancelled')")
             conn.commit()
             return cur.rowcount
         finally:

tests/test_video_download_pipeline.py

@@ -22,7 +22,7 @@ def test_classify_state():
     assert classify_state("InProgress") == "active"
     assert classify_state("Queued, Remotely") == "active"
     assert classify_state("Completed, Errored") == "failed"
-    assert classify_state("Completed, Cancelled") == "failed"
+    assert classify_state("Completed, Cancelled") == "cancelled"
     assert classify_state("Completed, TimedOut") == "failed"
     assert classify_state("") == "active"
 
@@ -112,9 +112,28 @@ def test_process_download_failed():
     assert upd["status"] == "failed"
 
 
-def test_process_download_no_transfer_yet():
+def test_process_download_cancelled():
     from core.video.download_monitor import process_download
-    assert process_download(_dl(), [], "/dl", lister=lambda d: [], mover=lambda s, d: None) is None
+    upd = process_download(_dl(), [_xfer("Completed, Cancelled")], "/dl",
+                           lister=lambda d: [], mover=lambda s, d: None)
+    assert upd["status"] == "cancelled"
+
+
+def test_process_download_missing_transfer_signals_missing():
+    from core.video.download_monitor import process_download
+    # slskd forgot it AND no file on disk → _missing (caller decides when to give up)
+    upd = process_download(_dl(), [], "/dl", lister=lambda d: [], mover=lambda s, d: None)
+    assert upd == {"_missing": True}
+
+
+def test_process_download_missing_but_file_present_completes():
+    from core.video.download_monitor import process_download
+    moved = {}
+    # slskd cleared the completed transfer (the music auto-clear) but the file is there
+    upd = process_download(_dl(), [], "/dl",
+                           lister=lambda d: ["/dl/Folder/movie.mkv"],
+                           mover=lambda s, d: moved.update(ok=True))
+    assert upd["status"] == "completed" and moved.get("ok") is True
 
 
 def test_process_download_completed_moves_file():